Arsonist's Lullabye
by Judith Wilcox
Summary: Mutants are on the verge of extinction. Earth has been left in ruins. The Sentinels have exterminated a majority of the mutant population and most of their human allies. Any survivors were rounded up, branded, and sent to labor camps. With what little hope they have, the Avengers and the remaining X-Men must come together in hopes of rewriting history and making a better future.


_All you have is your fire_  
 _And the place you need to reach_  
 _Don't you ever tame your demons_  
 _But always keep them on a leash_

-Arsonist's Lullabye; **by Hozier**

* * *

Opal remembered a time where the world was once a vibrant and colorful place. A world that was once filled with so much life, so much potential. The world that was once filled with people and animals and plants was currently dead. All the once vibrant colors were now various shades of brown, black, red, and grey. Earth served as a battlefield for mutants, humans, and Sentinels. A slight scowl came on Opal's face — _Sentinels_ brought a sour taste in her mouth. The very things that brought the downfall of the planet. The very things making mutants and humans go extinct. How could anyone think those _abominations_ would be OK? In the beginning, the governments of the world decided to reopen the Sentinel Program after a mutant assassinated a powerful political leader. Mutants had started rising after the whole New York fiasco with Loki; after they discovered a mutant was helping fight off the Chitauri, a lot of them decided to come out of the shadows. Not all of those mutants were friendly.

Looking back at that, Opal felt an overwhelming sense of responsibility and guilt. She felt responsible for the hostile mutants becoming more brazen with their crimes; she felt responsible for the political leader that got murdered as a result. It didn't matter what anyone else said, that was on _her_. _She_ fought with the Avengers in New York. _She_ created the world everyone was living in. _She_ was responsible for the deaths of millions, if not billions. That was when the guilt would set in. Opal Cunningham was responsible for countless deaths of innocent people. Countless mutants and their human allies, slaughtered by the Sentinels. Anyone — mutant or human — who managed to get captured were sent off to labor camps. All of that rested on Opal's conscious.

She hated herself more and more thinking about it.

Opal could remember the exact day news stations announced that the world was deciding they were looking into reintroducing the Sentinel Program. She wasn't quite aware on what it was — that had been the first time she ever heard of it. Thankfully, Tony had done some research and found out some scientist tried launching the program in the early 70s but got rejected. No one believed him, nor did they think giant robots would be the solution to handling a potential threat like _mutants_.

How was Opal supposed to live with herself, knowing she _un_ knowingly set in motion the end of the world and the eventual extinction of mutants and humans?

 _ **-0-0-0-0-**_

It had been years, since the first batch of Sentinels had been released worldwide. In the beginning, they were relatively easy to take down, but that didn't stop them from eliminating countless humans and mutants. The bodies of the slaughtered mutants had been gathered up — requested by the world's government — for experimentation. Countless hours of research, put in to find out how to improve the Sentinels; to keep them from being so easily manipulated by mutants and their human allies. A lot of the scientists went back to Bolivar Trask's — the man who started the Sentinel Program — findings and research. Trask had a _fascination_ with mutants. He loved figuring out how they worked. With his research, he started developing the Sentinels, in hopes of humanity being prepared for whatever threats the mutant community may pose.

Trask knew that the area he was going into was dangerous. In order for his research to progress, he needed test subjects, which meant he had to resort to his workers forcibly bringing him unwilling subjects for him to experiment on. The dark underbelly of the mutant community knew what Trask was up to, and a lot of them set out to kill him. Especially one. A blue-skinned, shapeshifter named Mystique. She was very bold, going to extreme lengths to kill him. Trask _loved_ her mutation — her ability to turn into anyone. And her aging process; from what little research Bolivar had on her, Mystique aged at a slower pace than most other mutants. Luckily, though, Trask's men were able to get a bit of blood sample from Mystique, after she tried assassinating him at the Paris Peace Accords. She narrowly missed him, but it was because of Mystique's brazenness that alerted humanity to the existence of mutants. It would be decades later when Opal Cunningham would truly bring them out of the shadows.

While the scientists had gone over Trask's work, they discovered something phenomenal. The research Trask had done with Mystique's blood sample. The data was, for the most part, complete, there were just a few tweaks that had to be done.

"If I'm reading this correctly," a scientist said, looking over the data carefully, "we should be able to apply this to the Sentinels. Once it's in place, they'll be able to adapt to any mutation on the planet."

 ** _-0-0-0-0-_**

"A Chinese monastery?" Natasha looked back at Opal with furrowed brows. "Are you _sure_ that's safe?"

Opal sighed. "It is for now," she said. "That's where Charles said to meet him and the others. I trust Charles, so..."

"And those Sentinels won't be able to detect us, right?" Steve asked, tapping his fingers on his shield anxiously. For the most part, the Quinjet had been able to fly undetected by the Sentinels. Mostly because of Tony's upgrades before things got _too_ bad.

"We've made it this far, haven't we?" Clint replied, a sarcastic lilt in his tone.

"Still doesn't mean they won't notice us eventually," was Steve's response.

"He's right," Opal replied. "As long as I'm with you guys, you're all targets. They'll still be able to sense me."

"And we made it clear you're not going anywhere by yourself." Thor's authoritative tone made Opal's shoulders hunch a little. When things started getting out of control, Opal suggested she leave to save the others. She already felt like shit for causing such an uproar, the last thing she wanted was to cause harm to her friends. She had to wonder if that would've been a good idea. Since the others refused to let her go off by herself, Opal had to see good people who were friends with someone in the Avengers perish. Maria, Rhodey, Fury's whereabouts were unknown, Opal could only assume something happened to Jane, Darcy, and Erik. It broke her heart.

"It would've been easier," she muttered.

"Going renegade wouldn't have solved anything," Bruce said.

"They would've still found you," Steve said. "And us...without even knowing what happened to you..."

"It's already my fault everything got like this," Opal exclaimed. "After what happened in New York...I honestly thought I was doing the right thing."

"We've told you before it's not your fault," Natasha said. "None of us could've predicted this."

That didn't ease the guilt in Opal's conscious. Not one bit.

* * *

 **(A/N):**

 **Sorry for the wait on this chapter, but here it is. This is a crossover with the AVENGERS and X-MEN: DAYS OF FUTURE PAST, but I did alter a few things. If anything seemed weird or confusing or whatever, don't hesitate to PM me and I'll try and clear it up the best I can. If you're interested in how this story will play out, don't hesitate to review, favorite, etc. Also, constructive criticism! I'm always a fan of that. Whatever you think needs improvement, let me know.**

 **MARVEL is not mine.**

 **Opal Cunningham is my OC from my story, I'M NOT OKAY (I PROMISE). It's a THOR story, and I haven't even started on the first AVENGERS story yet. She's paired up with Thor, though I'M NOT OKAY hasn't gotten into any romances yet. If you're interested in seeing what that story's about, go ahead and do so! At least so you're having an understanding on what she's like so far.**

 **One last thing, though, this kind of serves separately from the I'M OKAY story, but also connects to it? I know it doesn't make much sense, but once I start on the AVENGERS sequel for that story, it won't go off into an X-MEN universe, it'll follow the main MCU timeline. I don't know. I'm still working out the details on that.**

 **Leave a thought on anything that needs improvement.**

 **Thanks.**

 **Judith W**


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